hence possibly too weak to give strong FOLZ lines in the

central spot.

 If the accelerating potential of the microscope is

lowered, the FOLZ ring will move in toward the center of

the pattern. The scattering amplitude increases as the

ring moves in and the diffracted intensity consequently

increases (Steeds, 1979).


 4.2 Energy Dispersive Methods


 The use of energy dispersive x-ray analysis is a well

established means of characterizing the compositions of

materials on a microscale (Goldstein, 1979). The effects

of various experimental variables on the accuracy and

precision of the final EDS results are of paramount

importance. These effects have been reviewed extensively

elsewhere (Zaluzec, 1979). They are summarized here as 1)

instrument related, 2) specimen related, and 3) data

reduction related. Care must be taken in defining the

effects of all three if an accurate result is to be

obtained.

 Consider first the instrument and its effects.

Microscopes of the late 1970's vintage are generally less

than perfect experimental benches for x-ray

microanalysis. In unmodified instruments, many

uncollimated electrons and x-rays make their way to the

specimen environment where they then contribute to the

x-ray signals that are supposed to be generated only by